All smiles: The PM and German Chancellor greet each other in BerlinCredit: Getty Images

"I will be able to update Chancellor Merkel on where we are on our Brexit preparations," the Prime Minister said in a joint press conference with the German Chancellor, who wished her a "warm welcome" to Berlin.

The two leaders prepare for a press conferenceCredit: AP:Associated Press

A White House statement said: "The leaders agreed on the necessity of working collectively to move the transatlantic agenda forward, particularly on bringing stabilisation to the Middle East and North Africa, as well as securing diplomatic resolution to the conflicts in Syria and eastern Ukraine.

"The leaders also affirmed the importance of continued co-operation through multilateral institutions, including Nato."

Mr Obama said other countries should work with Mr Trump. He "urged his European counterparts to continue seeking solutions to common challenges with the incoming US administration on the basis of the core values that define the United States and Europe as open democracies", the White House added.

The talks today also highlighted the "grave concern" about the situation in Syria.

In a possible warning to Mr Putin, Mrs May said that the group were "united in our condemnation" of the situation in Syria and stressed the "need to keep up the pressure on Russia... including the possibility of sanctions on those who break international, humanitarian law".

They agreed that attacks against the rebel-held area of Aleppo should be halted immediately so humanitarian access to the city could be restored.